z16f2811 ZiLOG Semiconductor, z16f2811 Datasheet - Page 221

• Manufacturer Part Number: z16f2811
• Description: High Performance Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS022006-0207
When a Master loses arbitration, software is informed by means of the Arbitration Lost
interrupt. Software repeats the same transaction again at a later time.
A special case occurs when a slave transaction starts just before software attempts to start
a new master transaction by setting the
slave states before the START bit is set and the I
address match occurs and the I
cleared and an Arbitration Lost interrupt is asserted. Software minimizes the chance of this
occurring by checking the BUSY bit in the I2CSTATE register before initiating a master
transaction. If a slave address match does not occur, the Arbitration Lost interrupt does not
occur and the
once the I
Master Address Only Transactions
It is sometimes appropriate to perform an address-only transaction to determine if a
particular Slave device is able to respond. This transaction is performed by monitoring the
ACKV bit in the I2CSTATE register after the address has been written to the I2CDATA
register and the START bit has been set. Once ACKV is set, the ACK bit in the I2CSTATE
register determines if the Slave is able to communicate. The STOP bit must be set in the
I2CCTL register to terminate the transaction without transferring data. For a 10-bit slave
address, if the first address byte is acknowledged, the second address byte must also be
sent to determine if the appropriate slave is responding.
Another approach is to set both the STOP and START bits (for sending a 7-bit address).
Once both bits are cleared (7-bit address has been sent and transaction is complete), the
ACK
bit after the second TDRE interrupt (second address byte is being sent).
Master Transaction Diagrams
In the following transaction diagrams, shaded regions indicate data transferred from the
Master to the Slave and unshaded regions indicate data transferred from the Slave to the
Master. The transaction field labels are defined as follows:
•
•
•
•
•
Master Write Transaction with a 7-Bit Address
Figure 43
addressed Slave.
S — Start
W — Write
A — Acknowledge
A — Not Acknowledge
P — Stop
bit is read to determine if the slave is acknowledged. For a 10-bit slave, set the STOP
2
on page 208 illustrates the data transfer format from a Master to a 7-bit
C bus is no longer busy.
START
bit is not cleared. The I
P R E L I M I N A R Y
2
C Controller receives or transmits data, the
START
2
C Controller initiates the master transaction
bit. In this case the state machine enters the
2
C Controller does not arbitrate. If a slave
I2C Master/Slave Controller
Product Specification
ZNEO
™
START
Z16F Series
bit is
207